Possibly the most bizarrely convoluted reproductive cycle on the planet:

Things start to get complicated when you consider their life cycle. Let's start with a feeding animal living on a lobster's mouthparts: this individual – it's hard to assign a sex – can then produce one of three kinds of offspring: a "Pandora" larva, a "Prometheus" larva or a female.

The Pandora larva develops into another feeding adult – a straightforward case of asexual reproduction. By contrast, the female remains inside the adult and awaits a male – but, attentive readers will be crying, what male?

The answer lies in the Prometheus larva. This attaches itself to another feeding adult, then produces two or three males from within itself. These dwarf males, which are even more internally complex than the other stages, seek out the females and fertilise them – though the details are unknown.

Once the female has been fertilised, she leaves the adult's body and hunkers down in a sheltered region of the lobster's mouthparts. Her body, no longer needed, turns into a hard cyst. Inside this, a fertilised egg develops into yet another stage: the chordoid larva.

In due course this larva hatches and swims off to colonise another lobster. Once it has attached itself to one, it develops into another adult and the cycle begins again.

...Linnaeus's two-toed sloths Choloepus didactylus at the Estación Biológica Quebrada Blanco in north-eastern Peru have developed the delightful habit of climbing into an outdoor latrine building, seeking out the latrine contents AND EATING THEM ...

Apparently crows are quite a problem over there, because they use telegraph wires to build their nests. For a while there was a policy of destroying these nests. The crows then started to build decoy nests.

At just 1 millimetre long, the wasp Copidosoma floridanum hardly looks like it's the source of a devastating clone army that devours its victims from the inside out. The army can only manage this because it employs self-sacrificing child soldiers – having no prospect of growing to adulthood, they sacrifice themselves to protect their siblings.

This epic battle takes place inside a caterpillar called the cabbage looper, an agricultural pest that lays its eggs one at a time on the surfaces of leaves. Once laid the egg is vulnerable – if found by a female Copidosoma she will lay one or two eggs in it.

One egg might not sound so bad, but this is no ordinary egg. It is polyembryonic, meaning that the single embryo cell at its heart can repeatedly clone itself. As a result, just one egg can produce up to 2000 offspring....Once the host embryo develops into a caterpillar, the Copidosoma clones form an army. Yet the clones are not identical. Instead they are divided into castes, just like bees in a hive.

The most common caste of larvae is essentially maggots. They feed by drinking the host caterpillar's blood and, all being well, eventually emerge and become adult wasps. They are called reproductive larvae and there could be 1000 in a single caterpillar.

The second caste is the precocious larvae. These develop earlier than the reproductive larvae – hence their name – and they look quite different, with a thinner body and larger mandibles. They have no sex cells and will never become adults or reproduce. These are the child soldiers.

Copidosoma larvae may well find themselves sharing the caterpillar's body with competing parasites laid by another species of wasp. The precocious larvae are there to kill these competitors, and are produced in greater numbers if competitors are detected.

This turns out to be a pretty effective way of dealing with competing species, but the precocious larvae face other threats too. If more than one Copidosoma egg is laid in the same host, the two armies go to war.

Shaped like flying saucers, both males and females of the new jellyfish have gonads on the outsides of their bodies, unlike any of the approximately 3,000 other jellyfish species known to science .Gonads are the reproductive glands that produce sperm in males and eggs in females.Arranged in a "crater" at the center of the jellyfish's top side, the gonads, upon close inspection, resemble "skyscrapers in a downtown business district," said Lisa-Ann Gershwin, curator of zoology at the Queen Victoria Museum and Art Gallery in Launceston, Australia.

Yeah, I was wondering for a long time what was the deal with those flies who look kind of intact, but a bit bloated, and are dead on windows with a little smudge around them. Figuring out that the smudge was fungus that was filling the corpse, which in turn was attracting other flies for a bit of fungal necromancy was a revelation of sorts :)